JP2002353227A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To overcome a problem of a firing temperature increase when the protection film of a semiconductor device is formed of a lead glass. SOLUTION: A protection film 6 consisting of a resin having negative charge is formed on the oblique side 10 of a semiconductor substrate 1 comprising an n<+> -type semiconductor region 7, an n-type semiconductor region 8, and a p-type semiconductor region 9. The resin having a strong anionic functional group such as caboxyl, sulfo is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device, and more particularly, to a protective film most suitable for a semiconductor device having a mesa structure.

[0002]

2. Description of the Related Art A semiconductor element such as a diode or a transistor in which an outer peripheral surface of a semiconductor substrate is inclined, that is, a semiconductor element having a bevel structure or a mesa structure in which a pn junction of a semiconductor element is exposed is covered with a protective film. (Less than,
Bevel-shaped semiconductor elements) are known. In this type of bevel semiconductor device, the inclined surface is covered with a protective film made of lead-based glass or zinc-based glass to stabilize the semiconductor surface. These protective films, a well-known electrophoresis method, by printing a glass material in a bevel groove by a screen printing method, etc.,
Thereafter, the glass material is baked at a high temperature of 700 ° C. or higher to vitrify the glass material to form the glass material.

[0003]

However, the above-mentioned bevel semiconductor device has the following problems. (1) Since the glass material needs to be fired at a high temperature of 700 ° C. or more, there are many restrictions on the manufacturing process. That is, since the firing temperature is high, the glass protective film cannot be formed in the final step. (2) The semiconductor wafer is likely to warp due to the stress after the glass is formed, and the warpage of the wafer causes various inconveniences in the subsequent steps. That is, if the wafer is warped, there arises a problem in the process such that, for example, the wafer cannot be satisfactorily attracted to the vacuum chuck type stage. Also, if the degree of warpage of the wafer is large, problems such as the inability to follow the depth of focus of the exposure machine and the inability to obtain a uniform pattern profile within the wafer surface arise.

Accordingly, an object of the present invention is to provide a semiconductor device which can solve such a problem.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve the above-mentioned object, the present invention provides a semiconductor substrate comprising:
The present invention relates to a semiconductor element, wherein a protective film made of a resin having a negative charge is formed.

[0006]

The present invention has the following effects. (A) Since the protective film is made of a resin having a negative charge instead of a lead-based or zinc-based glass, high-temperature baking is not required at the time of forming the protective film, and a relatively low temperature (for example, 200 ° C.)
The heat treatment can form a protective film. As a result,
Restrictions on the manufacturing process of semiconductor elements are reduced, for example,
The protective film can be formed in the final step. (B) A protective film made of a resin having a negative charge has lower stress than a protective film made of glass. Therefore, the semiconductor substrate or the wafer does not warp after the formation of the protective film,
The inconvenience caused by the warpage of the substrate can be eliminated. That is. Since the substrate is unlikely to warp, for example, the substrate can be satisfactorily attracted to a vacuum chuck type stage, can follow the depth of focus of an exposure device, and can obtain a uniform pattern profile in the substrate or wafer surface. (C) It is possible to establish a manufacturing process that does not contain environmentally harmful elements such as lead and zinc. (D) Since the protective film has a negative charge, the negative charge captures mobile ions on the surface of the semiconductor substrate, resulting in a decrease in mobile positive ions. Therefore, instability of the withstand voltage due to the movable positive ions can be prevented. (E) Since the protective film is made of a resin having a negative charge, electrons near the surface of the n-type semiconductor region in contact with the protective film can be repelled into the bulk, and the depletion layer easily spreads in the n-type semiconductor region. Become. As a result, the withstand voltage of the element can be improved.

[0007]

1 and 2 show a bevel-type diode as a semiconductor device according to one embodiment of the present invention.
This will be described with reference to FIG. The bevel diode according to the present embodiment includes a semiconductor substrate 1 made of a silicon semiconductor, an anode electrode 3 formed on one main surface 2 of the semiconductor substrate 1 as a first electrode, and the other main electrode of the semiconductor substrate 1. It has a cathode electrode 5 as a second electrode formed on the surface 4 and a protective film 6 according to the present invention.

The silicon semiconductor substrate 1 includes an n ^{+ -type} semiconductor region 7 and an n ^{+ -type} semiconductor region 7 formed on the upper surface of the n ^{+ -type} semiconductor region 7.
It has a p-type semiconductor region 8 and a p-type semiconductor region 9 formed on the n-type semiconductor region 8.

An anode electrode 3 made of a metal material such as aluminum is formed on one main surface 2 of the semiconductor substrate 1 and has low resistance contact with the p-type semiconductor region 9. A cathode electrode 5 made of a metal material such as aluminum is formed on the other main surface 4 of the semiconductor substrate 1 and has low resistance contact with the n ^{+ type} semiconductor region 7.

The semiconductor substrate 1 has an inclined side surface 10.
The inclined side surface 10 is formed so as to widen from one main surface 2 to the other main surface 4 of the semiconductor substrate 1. The n-type semiconductor region 8 and the p-type semiconductor region 9 are formed on the inclined side surface (bevel groove) 10. The end of the pn junction 11 formed at the interface is exposed.

The protective film 6 according to the present invention is made of a resin having a negative charge, is provided so as to cover the inclined side surface 10 where the end of the pn junction 11 of the semiconductor substrate 1 is exposed, and has one end thereof. Extends to one main surface 2 of the semiconductor substrate 1 and covers the outer peripheral side of the one main surface 2 of the semiconductor substrate 1. This protective film can be solidified at a temperature lower than the firing temperature of the lead-based glass and the zinc-based glass, and exerts less stress on the semiconductor substrate 1 than the protective film of the lead-based glass and the zinc-based glass. Have

As a resin having a negative charge, a carboxyl group (—COO) is used as a side chain in a polymer constituting the resin.
H), a resin having a structure having a strongly anionic functional group such as a sulfonic acid group (—SO ₃ H), a halogen group, and an acid anhydride group can be used. The acid anhydride group can be represented by the following chemical formula (structural formula). Examples of the resin having a carboxyl group include polyacrylic acid,
The negatively charged resin having a sulfonic acid group is, for example, acrylamide sulfonic acid, the resin having a halogen group is, for example, a fluorinated aromatic polyimide, and the resin having an acid anhydride group is, for example, polyacrylic anhydride.

[0013]

Embedded image

In the present embodiment, polyacrylic acid is selected as the resin having a carboxyl group (—COOH) as the resin for the protective film 6.

When manufacturing the diode of FIG. 1, FIG.
As shown in FIG. 1, a plurality of diode type regions 12 are provided in a semiconductor wafer 1a, and a mesa groove 10a is provided between the semiconductor wafer 1a and the inclined side surface 10 so as to be obtained. After that, the coating resin is subjected to a heat treatment at 180 ° C. (preferably 200 ° C. or lower) to form the protective film 6. Thereafter, the wafer 1a is cut at a position indicated by a dotted line in FIG. 2 to obtain a plurality of diodes. When the zeta voltage of the protective film 6 made of a polyacrylic acid film was measured by asymmetric electrophoresis, it was -36 mV (PH =
7.1), and it was confirmed that the protective film 6 had a negative charge on the surface, that is, the surface was negatively charged.

According to the present embodiment, the effects (a), (b), (c), (d), and (e) shown in the above-described effects of the invention can be obtained.

[0017]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) The present invention can be applied not only to a diode but also to a semiconductor element such as a transistor. When manufacturing a transistor, for example, an n ^{+ -type} semiconductor region 20 as an emitter is provided in the p-type semiconductor region 9 in FIG. In FIG. 3, n ^{+ -type} semiconductor region 7 and n-type semiconductor region 8 function as collector regions, and p-type semiconductor region 9
Functions as a base region. Electrode 5 is a collector electrode,
The electrode 3 functions as an emitter electrode, and the electrode 21 functions as a base electrode. Note that an insulating film 22 such as an oxide film or a nitride film is provided on the outer peripheral side of the one main surface 2, and the same protective film 6 as that of FIG. The diode shown in FIG.
In FIG. 3, the equivalent to the insulating film 22 in FIG.
Can be formed in the same manner as described above. (2) The anode electrode 3 may be formed before or after forming the protective film 6. When the anode electrode 3 is formed after the protective film 6, the anode electrode 3 can be extended on the protective film 6. However,
After the formation of the anode electrode 3, a heat treatment for alloying the metal constituting the anode electrode and the silicon semiconductor (400)
~ 500 ° C), but some negatively charged resins cannot withstand this heat.
The formation of the anode electrode 3 is preferably performed before the formation of the protective film 6. (3) The heat treatment temperature of the protective film 6 is set to a temperature range lower than the firing temperature of the conventional glass material of about 700 ° C., for example, 150 to
Any temperature within 500 ° C. can be used.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a diode according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the diode of FIG. 1 in a wafer state.

FIG. 3 is a sectional view showing a transistor to which the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 3 Anode electrode 5 Cathode electrode 6 Protective film

Claims (1)

[Claims] 1. A semiconductor device, wherein a protective film made of a resin having a negative charge is formed on a surface of a semiconductor substrate.